The present invention relates to composite containers, and in particular relates to composite containers for vacuum packaging fragile products, such as potato crisps or cookie biscuits, and associated methods.
Food and drink products and other perishable items are often packaged in tubular containers that are sealed at both ends. For some time, it has been recognized that substantial economies, as well as environmental advantages, can be effected by the use of composite containers, as opposed to the traditional glass and metal containers. These composite containers typically include at least one structural body ply made of paperboard and are formed by wrapping a continuous strip of the body ply material around a mandrel of a desired shape to create a tubular structure. The body ply strip may be spirally wound around the mandrel or passed through a series of forming elements so as to be wrapped in a convolute shape around the mandrel. At the downstream end of the mandrel, the tube is cut into discrete lengths and fitted with end caps to form the container.
Tubular containers of this type typically include a liner ply on the inner surface of the paperboard body ply. The liner ply prevents liquids from leaking out of the container and also prevents liquids from entering the container and possibly contaminating the food product contained therein. Preferably, the liner ply is also resistant to the passage of gases so as to prevent odors of the food product in the container from escaping and to prevent atmospheric air from entering the container through the liner and spoiling the food product. The liner ply is often a laminate including kraft paper, aluminum foil and/or one or more polymer layers. Thus, the liner ply provides barrier properties and the body ply provides structural properties for the composite container.
In addition, a label ply is typically included and adhered to the outer surface of the paperboard body ply. The label ply, which is typically a paper based ply, is a source of information. The label carries the graphical matter that conveys product information, instructions, and regulatory compliance information. The label is also preferably decorative and aesthetically pleasing to the consumer, which enhances shelf appeal and increases consumer interest in the food product.
Certain food products benefit from being packaged while under a vacuum. Vacuum packaging removes oxygen from the space surrounding the product, which can improve the shelf life of the product within the package. This is especially true for perishable food products, or food products that may become stale if exposed to air. However, it is generally recognized that vacuum packaging in some tubular containers can only be accomplished with difficulty, if at all. Because of the structural design of the composite container, the application of vacuum to the interior of the container often results in partial or complete inward collapsing of the container walls along the length of the container. This can result in an unacceptable appearance for the composite container or an unacceptable sealing of the product within the container.
This problem is further discussed in U.S. Pat. No. 4,158,425, assigned to the assignee of the present invention and herein incorporated by reference. To avoid the partial or complete collapsing of the paperboard body ply of the container upon application of a vacuum inside the container, the container according to the ""425 patent has an impermeable or hermetically sealed liner secured interiorly to the container body solely at the opposed ends thereof with the major length of the liner being free of the tubular body so as to allow an inward contracting of the liner without the introduction of excessive stresses to the container body itself. A vacuum or reduced pressure atmosphere within the liner causes an inward deformation of the liner into contact with the product substantially independently of the surrounding container body. Thus, the stresses which are transferred to the container body are at the opposed ends thereof which are in turn rigidified by a pair of conventional end caps.
The ""425 patent, however, only addresses the problem of collapsing of the container walls. The ""425 patent does not discuss or provide a container designed to secure the food products during transportation. In particular, fragile food products, such as potato crisp or cookie biscuits, are extremely susceptible to breakage during transportation. These types of products are typically stacked within the container such that the products can move about the container during transportation. Although the ""425 patent provides an inwardly moving liner, it is directed to sealing the product for freshness without damaging the tubular body, and not directed to providing cushioning support to the food products in order to prevent damage during transportation.
Accordingly, there is a great need in the industry for a container that hermetically seals perishable food products, but that is also capable of protecting fragile food products during transportation. At the same time, however, such a container would also be capable of withstanding the rigors of vacuum packaging so as to increase the shelf life of the product and provide other benefits attendant to vacuum packaging.
These and other needs are provided, according to the present invention, by a tubular container having a flexible end closure secured to at least one of the opposed ends of the container that is free to move inwardly against food products contained therein when a vacuum is applied so as to provide cushioning support to the food products. As such, the food products are supported by a xe2x80x9cpillow-likexe2x80x9d cushion instead of a spaced metal end closure or other rigid surface as provided by current containers, thus preventing damage to the food products during transportation or inadvertent movement before the container is opened.
In particular, the container for vacuum packaging fragile food products, such as potato crisps, cookie biscuits, or baked wafers, includes a tubular body wall having opposed ends and inner and outer surfaces. The tubular body is formed using conventional spiral winding techniques known in the art, such as described in U.S. Pat. No. 4,158,425, which is assigned to the assignee of the present invention and herein incorporated by reference.
In one embodiment, a flexible liner that is impervious to the passage of liquids and gasses is also included. The flexible liner is secured to the respective ends of the tubular body by way of an adhesive band between the liner and the inner surface of the tubular body wall adjacent each end of the tubular body wall. As such, a free medial portion is defined between the opposed end portions of the liner that is free to move inwardly from the tubular body wall when vacuum is applied and then to move outwardly toward the inner surface of the tubular body wall when the container is opened and vacuum is lost. Although not necessary to practice the invention, the liner preferably comprises a flexible and stretchable liner formed of at least one polymeric layer without foil and paper layers. Other types of liner materials may also be used, such as liners comprising polymer/foil, kraft paper/foil/polymer, or kraft paper/foil laminates. Accordingly, the liner can move inwardly to substantially form to the contours of the food products contained therein, thus providing not only a hermetic seal but also cushioning support to the food products. In this manner, the vacuum created during packaging does not act directly on the body wall thus preventing inadvertent collapse of the body wall. When the container is opened, the vacuum is lost and the liner moves away from the food products such that the products may be removed. A label surrounds the outer surface of the body wall.
A vent hole can be formed through the body wall and the label, such as with a laser, for allowing the passage of air therethrough. The vent allows the medial portion of the liner to move inwardly against the food products and allows air to enter the cavity formed between the liner and the tubular body when vacuum is applied.
Advantageously, a flexible end closure is secured to at least one of the opposed ends of the tubular body. The flexible end closure moves inwardly against the food products contained within the tubular body when vacuum is applied so as to provide cushioning support to the food product. The flexible end closure includes a foil layer that is impervious to the passage of liquids and gasses, and in one embodiment, two flexible end closures are included for providing even further cushioning support to the food products.
Associated methods also form a part of the invention and, according to one embodiment, include the steps of forming a tubular body wall with opposed ends and a flexible liner adjacent the inner surface of the body wall, closing one end of the tubular body wall, and depositing the food products within the liner and tubular body wall. The vacuum packaging operation can then be performed by applying a negative pressure to the open end of the tubular body and then closing the open end of the tubular body with the flexible end closure. The negative pressure is then released such that the flexible liner is moved inwardly from the inner surface of the body wall against the food products, and the flexible end closure moves inwardly against the food products to provide cushioning support therefor.
Accordingly, and as is explained in more detail below, the Applicants have provided a new container for fragile food products which overcomes the disadvantages of conventional containers. The present invention is particularly advantageous for food products that are easily damaged during transportation, such as potato crisps or cookie biscuits. The new container is easy to open for consumers, and can use conventional body wall and label construction techniques, such as an overlapping or anaconda seam. At the same time, however, the present container is capable of withstanding the rigors of vacuum packaging so as to maintain a rigid shape and provide a hermetically sealed container to prevent air and moisture from contaminating the food products contained therein.